London apartment fire: Ominous warning of 'catastrophic event'

A massive fire has engulfed a 24-storey apartment building in London, with fears people are trapped inside.

It's now emerged those at the Grenfell Tower block had previously raised concerns about whether it was a fire risk, with a resident group speculating it would take "a catastrophic event" for the dangers to be acknowledged.

"Unfortunately, the Grenfell Action Group have reached the conclusion that only an incident that results in serious loss of life of [landlord] KCTMO residents will allow the external scrutiny to occur that will shine a light on the practices that characterise the malign governance of this non-functioning organisation," the group wrote in a blog post last November.

"It is our conviction that a serious fire in a tower block or similar high density residential property is the most likely reason that those who wield power at the KCTMO will be found out and brought to justice!"

Dozens of people are feared trapped in the blaze engulfing the apartment building early on Wednesday morning (local time), with video from the scene showing people appearing to leap from their windows to escape.

"And we will do everything in our power to ensure that those in authority know how long and how appallingly our landlord has ignored their responsibility to ensure the [health] and safety of their tenants and leaseholders."

More than 200 firefighters and 40 fire engines are at the scene, with the blaze reaching all the way from the second storey to the top floor.